System for control of superheat setpoint for hvac system

ABSTRACT

A refrigeration system includes a variable capacity compressor system configured to pressurize refrigerant within a refrigerant circuit and a controller configured to receive data indicative of an operating capacity of the variable capacity compressor system and configured to adjust a superheat target setpoint of the refrigerant within the refrigerant circuit based on the data.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from and the benefit of U.S.Provisional Application Ser. No. 62/720,798, entitled “SYSTEM FORCONTROL OF SUPERHEAT SETPOINT FOR HVAC SYSTEM” filed Aug. 21, 2018,which is hereby incorporated by reference in its entirety for allpurposes.

BACKGROUND

The disclosure relates generally to heating, ventilation, and airconditioning (HVAC) systems, and specifically, to controlling operationparameter setpoints of HVAC systems.

This section is intended to introduce the reader to various aspects ofart that may be related to various aspects of the present disclosure,which are described below. This discussion is believed to be helpful inproviding the reader with background information to facilitate a betterunderstanding of the various aspects of the present disclosure.Accordingly, it should be understood that these statements are to beread in this light, and not as admissions of prior art.

Environmental control systems are utilized in residential, commercial,and industrial environments to control environmental properties, such astemperature and humidity, for occupants of the respective environments.The environmental control system may control the environmentalproperties through control of an airflow delivered to and ventilatedfrom the environment. For example, an HVAC system may transfer heatbetween the airflow and refrigerant flowing through the system. The HVACsystem may flow the refrigerant through a circuit that includes certaintarget property setpoints for the refrigerant. The HVAC system may alsooperate at a certain capacity indicative of the heating and/or coolingability or capacity of the HVAC system based on components of the HVACsystem. In some HVAC systems, the heating and/or cooling capacity mayvary during operation.

SUMMARY

A summary of certain embodiments disclosed herein is set forth below. Itshould be understood that these aspects are presented merely to providethe reader with a brief summary of these certain embodiments and thatthese aspects are not intended to limit the scope of this disclosure.Indeed, this disclosure may encompass a variety of aspects that may notbe set forth below.

In one embodiment, a refrigeration system includes a variable capacitycompressor system configured to pressurize refrigerant within arefrigerant circuit and a controller configured to receive dataindicative of an operating capacity of the variable capacity compressorsystem and configured to adjust a superheat target setpoint of therefrigerant within the refrigerant circuit based on the data.

In one embodiment, a control system is configured to control operationof a vapor compression system, where the control system comprises amemory device and a processor, and where the memory device includesinstructions. The instructions, when executed by the processor, causethe processor to adjust an operating capacity of a variable capacitycompressor system disposed along a refrigerant circuit of the vaporcompression system and cause the processor to adjust a superheat targetsetpoint of a refrigerant flowing through the refrigerant circuit basedon the operating capacity.

In one embodiment, a vapor compression system includes a condenserdisposed along a refrigerant circuit and configured to condense arefrigerant flowing through the refrigerant circuit, a variable capacitycompressor system disposed along the refrigerant circuit and configuredto pressurize the refrigerant supplied to the condenser, and acontroller configured to adjust a superheat target setpoint of therefrigerant based on an operating capacity of the variable capacitycompressor system.

DRAWINGS

Various aspects of this disclosure may be better understood upon readingthe following detailed description and upon reference to the drawings inwhich:

FIG. 1 is a schematic of an environmental control for buildingenvironmental management that may employ one or more HVAC units, inaccordance with an aspect of the present disclosure;

FIG. 2 is a perspective view of an embodiment of an HVAC unit that maybe used in the environmental control system of FIG. 1, in accordancewith an aspect of the present disclosure;

FIG. 3 is a schematic of a residential heating and cooling system, inaccordance with an aspect of the present disclosure;

FIG. 4 is a schematic of an embodiment of a vapor compression systemthat can be used in any of the systems of FIGS. 1-3, in accordance withan aspect of the present disclosure;

FIG. 5 is a schematic of an embodiment of an HVAC system configured toadjust an operating capacity of the HVAC system via a variable capacitycompressor system, in accordance with an aspect of the presentdisclosure;

FIG. 6 is a diagram depicting properties of a refrigerant duringoperation of an embodiment of an HVAC system, in accordance with anaspect of the present disclosure; and

FIG. 7 is a block diagram of an embodiment of a method for adjustingoperations of an HVAC system based on an operating capacity, inaccordance with an aspect of the present disclosure.

DETAILED DESCRIPTION

One or more specific embodiments will be described below. In an effortto provide a concise description of these embodiments, not all featuresof an actual implementation are described in the specification. Itshould be appreciated that in the development of any such actualimplementation, as in any engineering or design project, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which may vary from one implementation toanother. Moreover, it should be appreciated that such a developmenteffort might be complex and time consuming, but would nevertheless be aroutine undertaking of design, fabrication, and manufacture for those ofordinary skill having the benefit of this disclosure.

The present disclosure is directed to heating, ventilation, and airconditioning (HVAC) systems that use a refrigerant circuit to transferheat between a refrigerant and an airflow. For example, the refrigerantcircuit includes an evaporator configured to transfer heat to therefrigerant, a condenser configured to remove heat from the refrigerant,and a compressor configured to pressurize the refrigerant. As usedherein, a refrigerant circuit may include any path that refrigerant mayflow therethrough, including a loop and/or a conduit. There may betarget setpoints for certain operating parameters of the HVAC system,such as parameters related to properties of the refrigerant flowingthrough the refrigerant circuit. Operation of components of the HVACsystem may be based on values of the target setpoints for certainoperating parameters.

As will be appreciated, the components of the HVAC system may include acertain operating capacity. The operating capacity for a component maybe indicative of a capability, such as a power, to heat and/or cool arefrigerant or an airflow. In some embodiments, the HVAC system may varythe heating and/or cooling capacity of the system by adjusting theoperation of certain components, such as a compressor system. Variationof component operating capacity may be based on airflow conditions, suchas a desired rate or a desired temperature of the airflow. For example,when a difference between a desired temperature of the airflow and acurrent temperature of the airflow is small and/or when a desired rateof conditioned airflow is low, decreasing an operating capacity of anHVAC system component, such as the compressor, may result in an increasein efficiency of the HVAC system. However, in certain existing systems,some operating parameter target setpoint values in the refrigerantcircuit are fixed regardless of the operational mode of the HVAC system.It is now recognized that maintaining the same target setpoint valueswhile varying the operating capacity of the HVAC system may affect theefficiency of the HVAC system.

Thus, in accordance with certain embodiments of the present disclosure,it is presently recognized that adjusting certain operating parametertarget setpoint values based on the operating capacity of the HVACsystem may enable the HVAC system to operate more efficiently.Specifically, adjusting the target setpoints for certain operationalparameters may result in an adjustment in the operation of certaincomponents of the HVAC system to further accommodate to the change inoperational settings and improve operating efficiency of the HVACsystem. For example, a target setpoint value for refrigeranttemperature, such as a superheat value, may be established for aparticular section or location of the refrigerant circuit. The HVACsystem is configured to measure and monitor the temperature of therefrigerant at the particular section of the refrigerant circuit andcompare the measured temperature to the target setpoint value. Operationof a component of the HVAC system, such as a condenser, heat exchanger,and/or compressor, may be adjusted to achieve and/or maintain therefrigerant temperature at the target setpoint value. The adjustment ofthe component operation may improve operating efficiency of the HVACsystem.

Turning now to the drawings, FIG. 1 illustrates a heating, ventilating,and air conditioning (HVAC) system for building environmental managementthat may employ one or more HVAC units. In the illustrated embodiment, abuilding 10 is air conditioned by a system that includes an HVAC unit12. The building 10 may be a commercial structure or a residentialstructure. As shown, the HVAC unit 12 is disposed on the roof of thebuilding 10; however, the HVAC unit 12 may be located in other equipmentrooms or areas adjacent the building 10. The HVAC unit 12 may be asingle packaged unit containing other equipment, such as a blower,integrated air handler, and/or auxiliary heating unit. In otherembodiments, the HVAC unit 12 may be part of a split HVAC system, suchas the system shown in FIG. 3, which includes an outdoor HVAC unit 58and an indoor HVAC unit 56.

The HVAC unit 12 is an air cooled device that implements a refrigerationcycle to provide conditioned air to the building 10. Specifically, theHVAC unit 12 may include one or more heat exchangers across which an airflow is passed to condition the air flow before the air flow is suppliedto the building. In the illustrated embodiment, the HVAC unit 12 is arooftop unit (RTU) that conditions a supply air stream, such asenvironmental air and/or a return air flow from the building 10. Afterthe HVAC unit 12 conditions the air, the air is supplied to the building10 via ductwork 14 extending throughout the building 10 from the HVACunit 12. For example, the ductwork 14 may extend to various individualfloors or other sections of the building 10. In certain embodiments, theHVAC unit 12 may be a heat pump that provides both heating and coolingto the building with one refrigeration circuit configured to operate indifferent modes. In other embodiments, the HVAC unit 12 may include oneor more refrigeration circuits for cooling an air stream and a furnacefor heating the air stream.

A control device 16, one type of which may be a thermostat, may be usedto designate the temperature of the conditioned air. The control device16 also may be used to control the flow of air through the ductwork 14.For example, the control device 16 may be used to regulate operation ofone or more components of the HVAC unit 12 or other components, such asdampers and fans, within the building 10 that may control flow of airthrough and/or from the ductwork 14. In some embodiments, other devicesmay be included in the system, such as pressure and/or temperaturetransducers or switches that sense the temperatures and pressures of thesupply air, return air, and so forth. Moreover, the control device 16may include computer systems that are integrated with or separate fromother building control or monitoring systems, and even systems that areremote from the building 10.

FIG. 2 is a perspective view of an embodiment of the HVAC unit 12. Inthe illustrated embodiment, the HVAC unit 12 is a single package unitthat may include one or more independent refrigeration circuits andcomponents that are tested, charged, wired, piped, and ready forinstallation. The HVAC unit 12 may provide a variety of heating and/orcooling functions, such as cooling only, heating only, cooling withelectric heat, cooling with dehumidification, cooling with gas heat, orcooling with a heat pump. As described above, the HVAC unit 12 maydirectly cool and/or heat an air stream provided to the building 10 tocondition a space in the building 10.

As shown in the illustrated embodiment of FIG. 2, a cabinet 24 enclosesthe HVAC unit 12 and provides structural support and protection to theinternal components from environmental and other contaminants. In someembodiments, the cabinet 24 may be constructed of galvanized steel andinsulated with aluminum foil faced insulation. Rails 26 may be joined tothe bottom perimeter of the cabinet 24 and provide a foundation for theHVAC unit 12. In certain embodiments, the rails 26 may provide accessfor a forklift and/or overhead rigging to facilitate installation and/orremoval of the HVAC unit 12. In some embodiments, the rails 26 may fitinto “curbs” on the roof to enable the HVAC unit 12 to provide air tothe ductwork 14 from the bottom of the HVAC unit 12 while blockingelements such as rain from leaking into the building 10.

The HVAC unit 12 includes heat exchangers 28 and 30 in fluidcommunication with one or more refrigeration circuits. Tubes within theheat exchangers 28 and 30 may circulate refrigerant, such as R-410A,through the heat exchangers 28 and 30. The tubes may be of varioustypes, such as multichannel tubes, conventional copper or aluminumtubing, and so forth. Together, the heat exchangers 28 and 30 mayimplement a thermal cycle in which the refrigerant undergoes phasechanges and/or temperature changes as it flows through the heatexchangers 28 and 30 to produce heated and/or cooled air. For example,the heat exchanger 28 may function as a condenser where heat is releasedfrom the refrigerant to ambient air, and the heat exchanger 30 mayfunction as an evaporator where the refrigerant absorbs heat to cool anair stream. In other embodiments, the HVAC unit 12 may operate in a heatpump mode where the roles of the heat exchangers 28 and 30 may bereversed. That is, the heat exchanger 28 may function as an evaporatorand the heat exchanger 30 may function as a condenser. In furtherembodiments, the HVAC unit 12 may include a furnace for heating the airstream that is supplied to the building 10. While the illustratedembodiment of FIG. 2 shows the HVAC unit 12 having two of the heatexchangers 28 and 30, in other embodiments, the HVAC unit 12 may includeone heat exchanger or more than two heat exchangers.

The heat exchanger 30 is located within a compartment 31 that separatesthe heat exchanger 30 from the heat exchanger 28. Fans 32 draw air fromthe environment through the heat exchanger 28. Air may be heated and/orcooled as the air flows through the heat exchanger 28 before beingreleased back to the environment surrounding the rooftop unit 12. Ablower assembly 34, powered by a motor 36, draws air through the heatexchanger 30 to heat or cool the air. The heated or cooled air may bedirected to the building 10 by the ductwork 14, which may be connectedto the HVAC unit 12. Before flowing through the heat exchanger 30, theconditioned air flows through one or more filters 38 that may removeparticulates and contaminants from the air. In certain embodiments, thefilters 38 may be disposed on the air intake side of the heat exchanger30 to prevent contaminants from contacting the heat exchanger 30.

The HVAC unit 12 also may include other equipment for implementing thethermal cycle. Compressors 42 increase the pressure and temperature ofthe refrigerant before the refrigerant enters the heat exchanger 28. Thecompressors 42 may be any suitable type of compressors, such as scrollcompressors, rotary compressors, screw compressors, or reciprocatingcompressors. In some embodiments, the compressors 42 may include a pairof hermetic direct drive compressors arranged in a dual stageconfiguration 44. However, in other embodiments, any number of thecompressors 42 may be provided to achieve various stages of heatingand/or cooling. As may be appreciated, additional equipment and devicesmay be included in the HVAC unit 12, such as a solid-core filter drier,a drain pan, a disconnect switch, an economizer, pressure switches,phase monitors, and humidity sensors, among other things.

The HVAC unit 12 may receive power through a terminal block 46. Forexample, a high voltage power source may be connected to the terminalblock 46 to power the equipment. The operation of the HVAC unit 12 maybe governed or regulated by a control board 48. The control board 48 mayinclude control circuitry connected to a thermostat, sensors, andalarms. One or more of these components may be referred to hereinseparately or collectively as the control device 16. The controlcircuitry may be configured to control operation of the equipment,provide alarms, and monitor safety switches. Wiring 49 may connect thecontrol board 48 and the terminal block 46 to the equipment of the HVACunit 12.

FIG. 3 illustrates a residential heating and cooling system 50, also inaccordance with present techniques. The residential heating and coolingsystem 50 may provide heated and cooled air to a residential structure,as well as provide outside air for ventilation and provide improvedindoor air quality (IAQ) through devices such as ultraviolet lights andair filters. In the illustrated embodiment, the residential heating andcooling system 50 is a split HVAC system. In general, a residence 52conditioned by a split HVAC system may include refrigerant conduits 54that operatively couple the indoor unit 56 to the outdoor unit 58. Theindoor unit 56 may be positioned in a utility room, an attic, abasement, and so forth. The outdoor unit 58 is typically situatedadjacent to a side of residence 52 and is covered by a shroud to protectthe system components and to prevent leaves and other debris orcontaminants from entering the unit. The refrigerant conduits 54transfer refrigerant between the indoor unit 56 and the outdoor unit 58,typically transferring primarily liquid refrigerant in one direction andprimarily vaporized refrigerant in an opposite direction.

When the system shown in FIG. 3 is operating as an air conditioner, aheat exchanger 60 in the outdoor unit 58 serves as a condenser forre-condensing vaporized refrigerant flowing from the indoor unit 56 tothe outdoor unit 58 via one of the refrigerant conduits 54. In theseapplications, a heat exchanger 62 of the indoor unit functions as anevaporator. Specifically, the heat exchanger 62 receives liquidrefrigerant, which may be expanded by an expansion device, andevaporates the refrigerant before returning it to the outdoor unit 58.

The outdoor unit 58 draws environmental air through the heat exchanger60 using a fan 64 and expels the air above the outdoor unit 58. Whenoperating as an air conditioner, the air is heated by the heat exchanger60 within the outdoor unit 58 and exits the unit at a temperature higherthan it entered. The indoor unit 56 includes a blower or fan 66 thatdirects air through or across the indoor heat exchanger 62, where theair is cooled when the system is operating in air conditioning mode.Thereafter, the air is passed through ductwork 68 that directs the airto the residence 52. The overall system operates to maintain a desiredtemperature as set by a system controller. When the temperature sensedinside the residence 52 is higher than the set point on the thermostat,or the set point plus a small amount, the residential heating andcooling system 50 may become operative to refrigerate additional air forcirculation through the residence 52. When the temperature reaches theset point, or the set point minus a small amount, the residentialheating and cooling system 50 may stop the refrigeration cycletemporarily.

The residential heating and cooling system 50 may also operate as a heatpump. When operating as a heat pump, the roles of heat exchangers 60 and62 are reversed. That is, the heat exchanger 60 of the outdoor unit 58will serve as an evaporator to evaporate refrigerant and thereby coolair entering the outdoor unit 58 as the air passes over the outdoor heatexchanger 60. The indoor heat exchanger 62 will receive a stream of airblown over it and will heat the air by condensing the refrigerant.

In some embodiments, the indoor unit 56 may include a furnace system 70.For example, the indoor unit 56 may include the furnace system 70 whenthe residential heating and cooling system 50 is not configured tooperate as a heat pump. The furnace system 70 may include a burnerassembly and heat exchanger, among other components, inside the indoorunit 56. Fuel is provided to the burner assembly of the furnace 70 whereit is mixed with air and combusted to form combustion products. Thecombustion products may pass through tubes or piping in a heatexchanger, separate from heat exchanger 62, such that air directed bythe blower 66 passes over the tubes or pipes and extracts heat from thecombustion products. The heated air may then be routed from the furnacesystem 70 to the ductwork 68 for heating the residence 52.

FIG. 4 is an embodiment of a vapor compression system 72 that can beused in any of the systems described above. The vapor compression system72 may circulate a refrigerant through a circuit starting with acompressor 74. The circuit may also include a condenser 76, an expansionvalve(s) or device(s) 78, and an evaporator 80. The vapor compressionsystem 72 may further include a control panel 82 that has an analog todigital (A/D) converter 84, a microprocessor 86, a non-volatile memory88, and/or an interface board 90. The control panel 82 and itscomponents may function to regulate operation of the vapor compressionsystem 72 based on feedback from an operator, from sensors of the vaporcompression system 72 that detect operating conditions, and so forth.

In some embodiments, the vapor compression system 72 may use one or moreof a variable speed drive (VSDs) 92, a motor 94, the compressor 74, thecondenser 76, the expansion valve or device 78, and/or the evaporator80. The motor 94 may drive the compressor 74 and may be powered by thevariable speed drive (VSD) 92. The VSD 92 receives alternating current(AC) power having a particular fixed line voltage and fixed linefrequency from an AC power source, and provides power having a variablevoltage and frequency to the motor 94. In other embodiments, the motor94 may be powered directly from an AC or direct current (DC) powersource. The motor 94 may include any type of electric motor that can bepowered by a VSD or directly from an AC or DC power source, such as aswitched reluctance motor, an induction motor, an electronicallycommutated permanent magnet motor, or another suitable motor.

The compressor 74 compresses a refrigerant vapor and delivers the vaporto the condenser 76 through a discharge passage. In some embodiments,the compressor 74 may be a centrifugal compressor. The refrigerant vapordelivered by the compressor 74 to the condenser 76 may transfer heat toa fluid passing across the condenser 76, such as ambient orenvironmental air 96. The refrigerant vapor may condense to arefrigerant liquid in the condenser 76 as a result of thermal heattransfer with the environmental air 96. The liquid refrigerant from thecondenser 76 may flow through the expansion device 78 to the evaporator80.

The liquid refrigerant delivered to the evaporator 80 may absorb heatfrom another air stream, such as a supply air stream 98 provided to thebuilding 10 or the residence 52. For example, the supply air stream 98may include ambient or environmental air, return air from a building, ora combination of the two. The liquid refrigerant in the evaporator 80may undergo a phase change from the liquid refrigerant to a refrigerantvapor. In this manner, the evaporator 38 may reduce the temperature ofthe supply air stream 98 via thermal heat transfer with the refrigerant.Thereafter, the vapor refrigerant exits the evaporator 80 and returns tothe compressor 74 by a suction line to complete the cycle.

In some embodiments, the vapor compression system 72 may further includea reheat coil in addition to the evaporator 80. For example, the reheatcoil may be positioned downstream of the evaporator relative to thesupply air stream 98 and may reheat the supply air stream 98 when thesupply air stream 98 is overcooled to remove humidity from the supplyair stream 98 before the supply air stream 98 is directed to thebuilding 10 or the residence 52.

It should be appreciated that any of the features described herein maybe incorporated with the HVAC unit 12, the residential heating andcooling system 50, or other HVAC systems. Additionally, while thefeatures disclosed herein are described in the context of embodimentsthat directly heat and cool a supply air stream provided to a buildingor other load, embodiments of the present disclosure may be applicableto other HVAC systems as well. For example, the features describedherein may be applied to mechanical cooling systems, free coolingsystems, chiller systems, or other heat pump or refrigerationapplications.

As discussed above, an HVAC system may have a capacity indicative of acapability of the HVAC system to heat and/or cool an airflow or otherfluid. The capacity is based on the operation of components of the HVACsystem, such as a compressor. In other words, operation of components ofthe HVAC system, such as compressors, may be adjusted to adjust thecapacity of the HVAC system. Additionally, the HVAC system may usetarget property setpoints for a refrigerant flowing through arefrigerant circuit in the HVAC system to control operation of the HVACsystem. That is, at different sections or locations along therefrigerant circuit, target values of certain properties for therefrigerant may be used and/or referenced, and operation of the HVACsystem be adjusted or otherwise controlled such that measured propertiesof the refrigerant approach or achieve the respective target values. Asdiscussed in detail below, such target property setpoints may beadjusted based on a current operational capacity of the HVAC system.

As an example, the HVAC system may set a superheat target setpoint, suchas a temperature, for the refrigerant between an outlet of an evaporatorand an inlet of a compressor and may adjust operation of certaincomponents of the HVAC system to cause the refrigerant between theoutlet of the evaporator and the inlet of the compressor to approach orachieve the superheat target setpoint. In certain embodiments, thesuperheat target setpoint may be a target refrigerant temperature or atarget amount of refrigerant superheat. The superheat target setpointmay be used or referenced to control operation of the HVAC system toachieve a desired suction temperature of the refrigerant, which is thetemperature of the refrigerant when entering the compressor. If thesuction temperature is outside of a certain range of temperatures, anefficiency or a performance of the compressor may be affected. As such,adjusting operation of the HVAC system based on the superheat targetsetpoint may result in a desirable suction temperature of therefrigerant to maintain a desirable performance of the compressor.Furthermore, based on the superheat target setpoint, operation of othercomponents of the HVAC system, such as condenser fans, may be modifiedto improve an efficiency of the HVAC system.

Although this disclosure primarily discusses adjustment of the superheattarget setpoint of the refrigerant based on an operational capacity ofthe HVAC system, it should be appreciated that adjustments of othersetpoints along the refrigeration circuit may be based on the capacityof the HVAC system. For example, target setpoints related to refrigeranttemperature downstream of the condenser and upstream of the expansiondevice, target setpoints related to refrigerant at a compressordischarge, target setpoints related to a position of the expansionvalve, another property setpoint, or any combination thereof may beadjusted based on an operational capacity of the HVAC system. As usedherein, “based on” includes embodiments where the adjustment of asetpoint is based at least on a current operating capacity of the HVACsystem. As should be understood, embodiments of this disclosure may beimplemented for packaged systems, split HVAC systems, or any othersuitable heating and cooling systems.

FIG. 5 is a schematic of an HVAC system 150 that includes a variablecapacity compressor system 152. The HVAC system 150 is configured toadjust a setpoint, such as a superheat target setpoint, based on anoperational capacity of the HVAC system 150. As illustrated in FIG. 5,the variable capacity compressor system 152 includes a first compressor154, a second compressor 156, and a third compressor 158, where eachcompressor 154, 156, and 158 is configured to pressurize vaporrefrigerant flowing through the HVAC system 150 at a particularcapacity. During operation, the HVAC system 150 may operate the first,second, and third compressors 154, 156, and 158 individually or in anycombination to operate the variable capacity compressor system 152 at adesired capacity. That is, the HVAC system 150 may operate any number ofthe compressors 154, 156, and 158, and the capacity of the variablecapacity compressor system 152 is adjusted based on which compressors154, 156, and 158 are operating. For example, the capacity of the HVACsystem 150 when all three compressors 154, 156, and 158 are operating isthe sum of the respective capacities of the three compressors 154, 156,and 158. It should be appreciated that each of the three compressors154, 156, and 158 may have different capacities or a same respectivecapacity.

After pressurization via the variable capacity compressor system 152,the saturation temperature of the refrigerant, or a temperature at whichthe refrigerant changes between a vapor and a liquid state, isincreased. Additionally, as a result of the pressurization of therefrigerant, the temperature of the refrigerant is increased. Therefrigerant then flows to a condenser 160 configured to cool therefrigerant. By way of example, the condenser 160 uses fans 162 to forceair, such as ambient air, across the condenser 160 to cool therefrigerant via convectional heat transfer. That is, heat from therefrigerant is rejected to the air forced across the condenser 160,which cools and condenses the refrigerant. When the refrigerant exitsthe condenser 160, the refrigerant may be a saturated liquid. In certainembodiments, the refrigerant may exit the condenser as a subcooledliquid at a subcooled temperature or a temperature below the saturationtemperature. The refrigerant then enters an expansion valve 164configured to decrease the pressure of the refrigerant. The temperatureof the refrigerant may be further reduced as a result of the decrease inpressure. The refrigerant then enters an evaporator 166 configured toexchange heat between the refrigerant and an airflow 168 flowing acrossthe evaporator 166. As the airflow 168 is warmer than the refrigerant,heat transfers from the airflow 168 to the refrigerant. Therefore, theairflow 168 is cooled, and the refrigerant is heated. The cooled airflow168 may then exit the evaporator 166 to cool areas conditioned by theHVAC system 150, such as the building 10. Meanwhile, the refrigerant maybe heated to a saturated vapor. In some embodiments, the refrigerant mayexit the evaporator 166 as a superheated vapor at a temperature abovethe saturation temperature of the refrigerant. The superheatedrefrigerant returns to the variable capacity compressor system 152 tobecome pressurized again and recirculate within the refrigerant circuit.

As mentioned, a suction temperature of the refrigerant returning to thevariable capacity compressor system 152 may affect performance of thevariable capacity compressor system 152. For example, there may be arange of suction temperatures at which the refrigerant may enter thevariable capacity compressor system 152 to achieve a desirableefficiency or performance. In certain embodiments, it may be desirablefor the refrigerant to enter the variable capacity compressor system 152above a certain temperature, such as a minimum suction temperature in arange of suction temperatures, such that the refrigerant is asuperheated vapor. This ensures that no liquid enters the variablecapacity compressor system 152, as liquid may affect a performance ofthe variable capacity compressor system 152. Additionally, it may bedesirable for the refrigerant to enter the variable capacity compressorsystem 152 below a certain temperature, such as a maximum suctiontemperature in a range of suction temperatures, to ensure the variablecapacity compressor system 152 performs as desired to compress therefrigerant. To this end, a superheat target setpoint, or a targetsuperheated temperature of the refrigerant, may be set to obtain adesired superheated temperature of the refrigerant that is within therange of desirable suction temperatures in order to improve and/oroptimize performance of the HVAC system 150.

While the temperature at which the refrigerant exits the evaporator 166is affected by the heat exchanged between the airflow 168 and therefrigerant within the evaporator 166, the amount of heat exchanged inthe evaporator 166 may be based primarily on a desired temperature ofthe airflow 168 exiting the evaporator 166, and provided to aconditioned space, instead of a desired temperature of the refrigerantentering the variable capacity compressor system 152. Accordingly, thetemperature of the refrigerant entering the evaporator 166 may beadjusted to affect the temperature of the refrigerant exiting theevaporator 166 after the refrigerant exchanges heat with the airflow 168in the evaporator 166.

In order to modify the temperature of the refrigerant entering theevaporator 166, operation of one or more components of the HVAC system150 may be adjusted. For example, an operation of the condenser 160 maybe adjusted. The condenser 160 may include coils through which thesuperheated refrigerant flows. The fans 162 of the condenser 160 forceor draw air across the coils to remove heat from the refrigerant. Thefans 162 may be operated in various stages. For example, one or more ofthe fans 162 may be operational, while one or more of the fans 162 maybe non-operational. Similarly, one or more of the fans 162 may bevariable speed fans. As will be appreciated, adjustment of the stagingof the fans adjusts a rate of airflow directed across the coils andtherefore adjusts an amount of heat removed from the refrigerant in thecondenser 160 to cool the refrigerant. In this way, operation of thecondenser 160 and the fans 162 can be modified to achieve a desiredtemperature of the refrigerant as the refrigerant exits the condenser160. For example, operation of the condenser 160 and the fans 162 may bemodified to achieve a target or desired amount of subcooling in therefrigerant exiting the condenser 160. In adjusting the temperature ofthe refrigerant leaving the condenser 160, the temperature of therefrigerant entering the evaporator 166 and leaving the evaporator 166may be ultimately adjusted and controlled.

It should be appreciated that, in certain embodiments, operations ofother components of the HVAC system 150 may be adjusted to effectuate achange in the refrigerant temperature at different stages or locationsalong the refrigerant circuit. By way of example, a position of theexpansion valve 164 may be adjusted to modify the temperature of therefrigerant entering the evaporator 166 and/or leaving the evaporator166.

As will be appreciated, adjusting the operation of the variable capacitycompressor system 152, and thus the capacity of the HVAC system 150, maycause a change in the saturation temperature of the refrigerant and/or adischarge temperature of the refrigerant exiting the variable capacitycompressor system 152. For example, when operation of the variablecapacity compressor system 152 is adjusted from a low capacity to a highcapacity, the pressure of the refrigerant exiting the variable capacitycompressor system 152 and entering the condenser 160 increases.Accordingly, a saturated condensing temperature of the refrigerant alsoincreases. The increase in saturated condensing temperature may furtherresult in a higher temperature of the refrigerant exiting the condenser160. Therefore, in the manner described above, the temperature of therefrigerant entering and exiting the evaporator 166 may be ultimatelyaffected by the change in refrigerant properties at the condenser 160that are caused by the change in operating capacity of the variablecapacity compressor system 152.

The increase in saturated condensing temperature of the refrigerant mayalso result in a different amount of cooling utilized to condense therefrigerant into a saturated or subcooled liquid in the condenser 160.As described in detail below, due to the refrigerant property changeseffectuated by a change in the operating capacity of the variablecapacity compressor system 152, one or more target setpoints of the HVACsystem 150 may be adjusted. Additionally, one or more components of theHVAC system 150 may correspondingly be adjusted to improve an efficiencyof the HVAC system 150.

To control the operation of the components, the HVAC system 150 mayinclude and/or be in communication with a controller 170. The controller170, which may be similar to the control panel 82, may include a memory172 and a processor 174. The memory 172 may be a mass storage device, aflash memory device, removable memory, or any other non-transitorycomputer-readable medium that includes instructions regarding control ofthe HVAC system 150. The memory 172 may also include volatile memorysuch as randomly accessible memory (RAM) and/or non-volatile memory suchas hard disc memory, flash memory, and/or other suitable memory formats.The processor 174 may execute the instructions stored in the memory 172,such as instructions to adjust operation of the variable capacitycompressor system 152, the condenser 160, the fans 162, the expansionvalve 164, or any other component of the HVAC system 150.

The controller 170 may be in communication with multiple sensors. Forexample, in the illustrated embodiment, a first sensor 176 is configuredto measure the suction temperature of the refrigerant, a second sensor178 is configured to measure the discharge temperature and/or pressureof the refrigerant exiting the variable capacity compressor system 152,and a third sensor 180 is configured to measure the temperature of therefrigerant exiting the condenser 160. In some embodiments, the HVACsystem 150 also includes a fourth sensor 182 configured to measure thetemperature and/or pressure of the refrigerant downstream of theexpansion valve 164 and upstream of the evaporator 166. The controller170 may use the sensors 176-182 to determine operational adjustments tocomponents of the HVAC system 150. The operational adjustments tocomponents of the HVAC system 150 may also be based an adjustment to thesuperheat target setpoint that is modified based on the operationalcapacity of the HVAC system 150.

For example, the controller 170 may use the first sensor 176 to monitorthe suction temperature of the refrigerant to determine if therefrigerant entering the variable capacity compressor system 152 is atthe superheat target setpoint and/or whether operation of any componentsof the HVAC system 150 should be modified. In some embodiments, thefirst sensor 176 may be used to detect a pressure of the refrigerantentering the variable capacity compressor system 152, which may be usedto determine the saturation temperature of the refrigerant.

The controller 170 may use the second sensor 178 to determine thetemperature of the refrigerant prior to entering the condenser 160 todetermine a desired amount of cooling to be performed via the condenser160. For example, the controller 170 may compare a measured temperatureof the refrigerant received from the second sensor 178 with thesaturated condensing temperature of the refrigerant to determine theamount of cooling desired for the refrigerant. The controller 170 mayuse the third sensor 180 to detect the temperature of the refrigerantexiting the condenser 160. The measurement of the third sensor 180 maybe further used by the controller 170 to determine whether operationaladjustment of the condenser 160 is desired to adjust the temperature ofthe refrigerant exiting the condenser 160.

The controller 170 may use the fourth sensor 182 to detect thetemperature entering the evaporator 166. The measurement of the fourthsensor 182 may be further used by the controller 170 to adjust operationof the expansion valve 164 to achieve a desired temperature of therefrigerant upstream of the evaporator 166. It should be appreciatedthat the HVAC system 150 may include additional sensors, and any sensorof the HVAC system 150 may measure any appropriate parameter of the HVACsystem 150 to determine whether adjustment in the operation of anycomponents of the HVAC system 150 is desirable.

Although FIG. 5 illustrates the variable capacity compressor system 152as including three compressors 154, 156, and 158, there may be anysuitable number of compressors in the HVAC system 150. Additionally, incertain embodiments, the variable capacity compressor system 152includes a number of variable capacity compressors, which are eachconfigured to adjust an individual capacity during operation. In thismanner, the variable capacity compressor system 152 may include onevariable capacity compressor capable of adjusting the capacity of theHVAC system 150. Additionally, it should be appreciated that the HVACsystem 150 may include several refrigerant circuits, each with separateevaporator and/or condenser coils, and one or more compressors. As such,the capacity of the HVAC system 150 may be based on the operation of therespective refrigerant circuits. Additionally, separate superheat targetsetpoints may be set for each respective refrigerant circuit. To thisend, operational adjustments for the respective components of eachrefrigerant circuit may be individually controlled.

FIG. 6 illustrates properties of a refrigerant during operation of theHVAC system 150. Specifically, the illustrated embodiment includes afirst scale 250 of a first performance parameter of the HVAC system 150and a second scale 252 of a second performance parameter of the HVACsystem 150. The first scale 250 illustrates performance parameter valuesof the refrigerant during operation of the HVAC system 150 at a firstcapacity or first compressor capacity. The second scale 252 illustratesperformance parameter values of the refrigerant during operation of theHVAC system 150 at a second capacity or compressor capacity that isgreater than the first capacity represented with the first scale 250.Comparison of the first and second scales 250 and 252 illustratesdifferences in the operation of the HVAC system 150 and refrigerantproperties at different operating capacities of the HVAC system 150. Inparticular, the discussion below is focused on refrigerant temperaturewithin the HVAC system 150 at different operating capacities of the HVACsystem 150 and the associated operation of the HVAC system 150. In otherwords, the first and second scales 250 and 252 described below representvariations in refrigerant temperature at first and second operatingcapacities, respectively, of the HVAC system 150.

The first scale 250 represents refrigerant temperature at differentpoints along the refrigerant circuit of the HVAC system 150 duringoperation of the HVAC system 150 at a first capacity. For example, thefirst scale 250 shows a first saturated vapor temperature 254 indicativeof a temperature of the refrigerant at which the refrigerant iscompletely vaporized, where an increase in pressure and/or a decrease intemperature of the refrigerant will cause at least a portion of therefrigerant to change from a vapor to a liquid. In certain embodiments,the saturated vapor temperature of the refrigerant is based on acapacity or compressor capacity of the HVAC system 150. Indeed,increasing the first capacity or first compressor capacity of the HVACsystem 150 may increase the first saturated vapor temperature 254 of therefrigerant within the HVAC system 150. Since the variable capacitycompressor system 152 is configured to increase pressure of therefrigerant, it may be desirable for the refrigerant to enter thevariable capacity compressor system 152 at a first superheatedtemperature 256, which is a temperature greater than the first saturatedvapor temperature 254, to ensure that liquid is not formed after thevariable capacity compressor system 152 has increased the pressure ofthe refrigerant. For example, the first superheated temperature 256 maybe greater than the first saturated vapor temperature 254 by a firstsuperheat amount 258, such as 10° C. In some embodiments, an adjustmentto the first saturated vapor temperature 254, such as via a change inoperational capacity of the HVAC system 150, may result in a similaradjustment to the first superheated temperature 256 to maintain adesired or target magnitude of the first superheat amount 258.

There may be a first range of superheated temperatures 260 at which therefrigerant may enter the variable capacity compressor system 152 foreffective and/or efficient operation. The first range of superheatedtemperatures 260 may include a first minimum superheated temperature 262and/or a first maximum superheated temperature 264, which may bedetermined based on capabilities of the variable capacity compressorsystem 152. Therefore, the first superheated temperature 256 may bewithin in first range of superheated temperatures 260. In other words,the first superheated temperature 256 may be between the first minimumsuperheated temperature 262 and the first maximum superheatedtemperature 264. It should be appreciated that, although a selectedsuperheated target setpoint may be between the minimum superheatedtemperature 262 and the maximum superheated temperature 264, thesuperheated target setpoint may not be in the exact average of theminimum superheated temperature 262 and the maximum superheatedtemperature 264. For example, it may be more desirable to achieve alower superheated temperature of the refrigerant and thus, thesuperheated target setpoint may be more proximate to the minimumsuperheated temperature 262 than the maximum superheated temperature264.

The temperature of the refrigerant may approach or achieve the firstsuperheated temperature 256 when heat is added to the refrigerant in theevaporator 166. Specifically, the refrigerant may enter the evaporator166 at a first chilled temperature 266 and may absorb heat from theairflow 168. The heat from the airflow 168 may raise the temperature ofthe refrigerant by a first heating amount 268. As will be appreciated,the HVAC system 150 is configured to operate to enable the refrigerantto reach the first superheated temperature 256 when the first heatingamount 268 is added to the refrigerant within the evaporator 166.

It should be understood the first heating amount 268 may be based on adesired temperature of the airflow 168. For example, the first heatingamount 268 may be determined via building occupancy setpoints of desiredtemperatures for areas conditioned by the HVAC system 150. In otherwords, a magnitude of the first heating amount 268 applied to therefrigerant, and therefore removed from the airflow 168, may be based adesired temperature of the airflow 168 cooled by the evaporator 166,which may be based on a target temperature of a conditioned spaceserviced by the HVAC system 150. Thus, the first heating amount 268 maynot directly depend on target temperature setpoints of the refrigerantitself.

Therefore, to achieve the first superheated temperature 256, a desiredor targeted value of the first chilled temperature 266 entering theevaporator 166 may be determined based on an expected value of the firstheating amount 268. In particular, a targeted value of the first chilledtemperature 266 of the refrigerant may be selected that will enable therefrigerant to achieve the first superheated temperature 256 uponapplication of the first heating amount 268 to the refrigerant in theevaporator 166. In certain embodiments, the magnitude of the firstchilled temperature 266 entering the evaporator 166 may be adjusted byadjusting operation of other components of the HVAC system 150. Forexample, the magnitude of the first chilled temperature 266 may beadjusted by adjusting an amount that the refrigerant is cooled by thecondenser 160 and/or by the expansion valve 164. Thus, to adjust thevalue of the first chilled temperature 266, operation of the condenser160 and/or the expansion valve 164 may be adjusted accordingly. Forexample, the fans 162 of the condenser 160 may be operated at adifferent speed and/or the expansion valve 164 may be set at a differentposition in order cause the refrigerant to approach or reach a differentvalue of the first chilled temperature 266 upon entering the evaporator166. In other words, adjusting operation of the condenser 160 and/or theexpansion valve 164 effectuates an adjustment to the first chilledtemperature 266 of the refrigerant entering the evaporator 166.

If the first heating amount 268 is unchanged, then adding the firstheating amount 268 to the adjusted value of the first chilledtemperature 266 generates an adjusted value for the first superheatedtemperature 256. In this manner, the operation of the condenser 160and/or the expansion valve 164 may be adjusted in order to ultimatelyadjust the superheated temperature of refrigerant entering the variablecapacity compressor system 152.

In certain embodiments, the first heating amount 268 may change. Forexample, based on an adjusted thermostat set point for a conditionedspaced served by the HVAC system 150, a desired temperature of theairflow 168 cooled by the evaporator 166 may change. As a result, thefirst heating amount 268 transferred from the airflow 168 to therefrigerant in the evaporator 166 may change. If the first heatingamount 268 is changed, operation of the HVAC system 150 may still beadjusted, in the manners described above, in order to achieve aparticular value of the first chilled temperature 266 of the refrigerantentering the evaporator 166 that will enable the refrigerant to approachor attain the first superheated temperature 256 upon application of theadjusted first heating amount 268 to the refrigerant.

As mentioned above, the second scale 252 represents refrigeranttemperatures at various points along the refrigerant circuit when theHVAC system 150 is operating at a second operational capacity that isgreater than the first operational capacity. An increase in thecompressor capacity of the HVAC system 150 causes the saturationtemperature of the refrigerant to increase. For example, the compressorcapacity of the HVAC system 150 may be increased such that the firstsaturated vapor temperature 254 increases by a first amount 270 to asecond saturated vapor temperature 272. Due to the increase in therefrigerant saturation temperature to the second saturated vaportemperature 272, it may be desirable to increase the first superheatedtemperature 256, or superheat target temperature, by a second amount 274to a second superheated temperature 276. In other words, it may bedesirable to provide the refrigerant to the variable capacity compressorsystem 152 with a second superheat amount 278 above the second saturatedvapor temperature 272 to ensure that no liquid refrigerant enters and iscompressed by the variable capacity compressor system 152. In someembodiments, the second superheat amount 278 is approximately the sameas the first superheat amount 258. In other words, the amount ofsuperheat that it is desirable for the refrigerant to have as therefrigerant enters the variable capacity compressor system 152 may beconstant for multiple different operating capacities of the HVAC system150. In other embodiments, the amount of superheat targeted for therefrigerant entering the variable capacity compressor system 152 mayvary as the operating compressor capacity of the HVAC system 150 varies.

The second superheated temperature 276 may be in a second range ofsuperheated temperatures 280 that includes a second minimum superheatedtemperature 282 and a second maximum superheated temperature 284. Insome embodiments, the range of superheated temperatures may be adjustedbased on a change to the saturated vapor temperature caused by variationin operational or compressor capacity of the HVAC system 150.

At the second operational capacity or compressor capacity of the HVACsystem 150, a second heating amount 286 may be added to the refrigerantas the refrigerant passes through the evaporator 166. As similarlydiscussed above, the magnitude of the second heating amount 286 may bebased on a desired temperature of the airflow 168. If an expected valueof the second heating amount 286 is known, calculated, or otherwisedetermined, the temperature of the refrigerant entering the evaporator166 may be adjusted accordingly to cause the refrigerant to approach orattain the second superheated temperature 276 when the second heatingamount 286 is added to the refrigerant in the evaporator 166.

As the value of the second superheated temperature 276, or targetsuperheat temperature setpoint, increases for the second operationalcapacity represented by scale 252, a target temperature value of therefrigerant entering the evaporator 166 may correspondingly beincreased. For example, the value of the first chilled temperature 266shown in the first scale 250 may be increased by a third amount 288 to asecond chilled temperature 290 value. In some embodiments, operation ofthe condenser 160 and/or the expansion valve 164 may be adjusted suchthat refrigerant approaches or reaches the second chilled temperature290 at the refrigerant enters the evaporator 166. For example, the fans162 of the condenser 160 may be operated at lower speeds to effectuateless cooling of the refrigerant at the condenser 160. The reducedcooling of the refrigerant at the condenser 160 may enable therefrigerant to enter the evaporator 166 at the second chilledtemperature 290 instead of, for example, the lower first chilledtemperature 266. In this manner, operation of the HVAC system 150 may bemore efficient. Specifically, the amount of power consumed by the fansduring operation of the condenser 160 may be decreased when theoperational capacity or compressor capacity of the HVAC system 150 isincreased, while still superheating the refrigerant entering thevariable capacity compressor system 152 by a desired amount.

It should be appreciated that, in certain embodiments, the first amount270, the second amount 274, and the third amount 288 may beapproximately the same. In other words, the superheated temperature ofrefrigerant entering the compressor and the chilled temperature ofrefrigerant entering the evaporator may be adjusted by an amount that isapproximately the same as an amount that the saturation temperature ofthe refrigerant is adjusted by virtue of the increase in compressorcapacity. In additional or alternative embodiments, the superheatedtemperature target setpoint and/or the chilled temperature targetsetpoint may be adjusted by an amount different from the amount by whichthe saturation temperature of the refrigerant is adjusted. For example,the superheated temperature target setpoint and/or the chilledtemperature target setpoint may be adjusted by a multiple of or anoffset of the amount by which the saturation temperature is adjusted.

It should also be understood that, in certain embodiments, thesuperheated temperature, such as the second superheated temperature 276,may be a target setpoint that is based on the operational capacity orcompressor capacity of the HVAC system 150. That is, when theoperational capacity or compressor capacity of the HVAC system 150 isadjusted, the target temperature of the refrigerant exiting theevaporator 166 is also adjusted. In additional or alternativeembodiments, the superheat amount, such as the second superheat amount278, may be a target setpoint value that is based on the operationalcapacity or compressor capacity. In other words, when the operationalcapacity or compressor capacity of the HVAC system 150 is adjusted, thetarget amount by which the refrigerant is heated above the saturationtemperature when exiting the evaporator 166 may be adjusted.

To illustrate adjustment in the operation of the HVAC system 150 inaccordance with present techniques, FIG. 7 is a block diagram of anembodiment of a method 350 for adjusting operating parameter setpoints,such as superheat temperature or superheat amount setpoints, based on acapacity of the HVAC system 150. At block 352, a change of operation ofthe HVAC system 150 is detected. For example, an adjustment to theoperation of a particular component, such as the variable capacitycompressor system 152, may be monitored and detected. In one embodiment,operation of the variable capacity compressor system 152 may be adjustedin response to a change in desired temperature of an airflow supplied bythe HVAC system 150 and/or in response to a change in ambienttemperature.

The change in operation of the particular component, such as thevariable capacity compressor system 152, may result in the HVAC system150 operating at a different operational capacity or compressorcapacity. At block 354, the new capacity is determined. As discussedabove, the capacity may depend on desired operations of components ofthe HVAC system 150. In some embodiments, the variable capacitycompressor system 152 may operate at different capacities. Thedetermination of the new operating capacity may include a determinationof the operational mode, stage, or other operating parameter of thevariable capacity compressor system 152. In additional or alternativeembodiments, operations of additional components of the HVAC system 150may also be monitored to determine the total operating capacity of theHVAC system 150.

At block 356, an operational parameter setpoint value is adjusted. Morespecifically, the operational parameter setpoint value is adjusted basedon the new capacity of HVAC system 150 operation determined in block354. As discussed in detail above, the operational parameter setpointmay be a superheat temperature target setpoint or a superheat amounttarget setpoint. However, it should be appreciated that the operationalparameter setpoint may be indicative of or related to another suitableoperational parameter, such as a target suction temperature ofrefrigerant, a target subcooled temperature of refrigerant, or any othertarget refrigerant temperature at any suitable location along therefrigerant circuit of the HVAC system 150.

In the manner described above, adjustment of a particular refrigeranttemperature setpoint value, and subsequent, consequential HVAC system150 operation, may ultimately result in an adjustment of otherrefrigerant temperatures within the HVAC system 150. In particular,adjustment of a particular refrigerant temperature setpoint value mayenable control of an amount of superheat or a superheat temperature ofrefrigerant exiting the evaporator 166.

The temperature setpoint value may be adjusted based at least on thenewly determined capacity of the HVAC system 150. For example, theparticular refrigerant temperature setpoint value may be proportionallyadjusted based on the change in operating capacity of the HVAC system150. In other embodiments, the adjustment to the refrigerant temperaturesetpoint value may be based on a percentage of the newly-determinedoperating capacity relative to a maximum operating capacity of the HVACsystem 150. In another embodiment, the adjustment to the refrigeranttemperature setpoint value may be based on an algorithm, a lookup tableof capacities and setpoints, and/or other factors in addition to achange in operating capacity of the HVAC system 150.

Based on the adjustment to the operational parameter setpoint value, theoperation of the HVAC system 150 is further adjusted to achieve the newoperational parameter setpoint, as shown at block 358. For example,based on an adjustment to a target superheat temperature of refrigerantexiting the evaporator 166, operation of the HVAC system 150 may bemodified to cause the refrigerant exiting the evaporator 166 to approachor achieve the new target superheat temperature. As previouslydiscussed, components of the HVAC system 150, such as the condenser 160,fans of the condenser 160, the expansion valve 164, the variablecapacity compressor system 152, another suitable component, or anycombination thereof, may be adjusted to cause the refrigerant toapproach or reach the new target superheat temperature. As discussedabove, certain adjustments to the operation of the HVAC system 150, suchas a decrease in condenser 160 fan speed or power based on an increasein the capacity of the variable capacity compressor system 152 or HVACsystem 150 may result in more efficient operation of the HVAC system150.

After the operation of the HVAC system 150 is adjusted, the steps ofblocks 352 and 354 may be repeated to determine if the HVAC system 150operation adjustment results in a new operational capacity of the HVACsystem 150. As such, the steps of the method 350 may be repeated toiteratively achieve a target operational value corresponding to aparticular operational capacity.

In some embodiments, the steps of the method 350 are adjusted via thecontroller 170. Moreover, it should be appreciated that the stepsdescribed in the method 350 are not exclusive. Indeed, additional stepsmay be performed in the method 350, such as after block 358 or inbetween any of the blocks 352-358 of the method 350. Furthermore, incertain embodiments, some of the aforementioned steps may not beperformed during execution of the method 350.

As set forth above, embodiments of the present disclosure may provideone or more technical effects useful in the operation of HVAC systems.For example, an operational parameter setpoint value, such as atemperature setpoint of refrigerant, may be adjusted based on anoperating capacity of an HVAC system. Based on the adjustment in theoperational parameter setpoint value, operation of the HVAC system isfurther adjusted. The additional adjustment in operation of the HVACsystem may result in more efficient operation of the HVAC system 150.For example, the disclosed embodiments include an HVAC system configuredto adjust a refrigerant temperature setpoint value, such as a superheattemperature or superheat amount, based on a change in operationalcapacity of a variable capacity compressor system of the HVAC system150. In response to the refrigerant temperature setpoint valueadjustment, components of the HVAC system, such as condenser fans, mayalso adjust operation to cause the refrigerant to approach or achievethe new temperature setpoint value. As discussed above, such adjustmentto the operation of HVAC system components improves operation the HVACsystem and increases efficiency of HVAC system operation. The technicaleffects and technical problems in the specification are examples and arenot limiting. It should be noted that the embodiments described in thespecification may have other technical effects and can solve othertechnical problems.

While only certain features and embodiments of the disclosure have beenillustrated and described, many modifications and changes may occur tothose skilled in the art, such as variations in sizes, dimensions,structures, shapes and proportions of the various elements, values ofparameters, mounting arrangements, use of materials, colors,orientations, and the like, without materially departing from the novelteachings and advantages of the subject matter recited in the claims.The order or sequence of any process or method steps may be varied orre-sequenced according to alternative embodiments. It is, therefore, tobe understood that the appended claims are intended to cover all suchmodifications and changes as fall within the true spirit of thedisclosure. Furthermore, in an effort to provide a concise descriptionof the exemplary embodiments, all features of an actual implementationmay not have been described, such as those unrelated to the presentlycontemplated best mode of carrying out the disclosed embodiments, orthose unrelated to enabling the claimed embodiments. It should beappreciated that in the development of any such actual implementation,as in any engineering or design project, numerous implementationspecific decisions may be made. Such a development effort might becomplex and time consuming, but would nevertheless be a routineundertaking of design, fabrication, and manufacture for those ofordinary skill having the benefit of this disclosure, without undueexperimentation.

1. A refrigeration system, comprising: a variable capacity compressorsystem configured to pressurize refrigerant within a refrigerantcircuit; and a controller configured to receive data indicative of anoperating capacity of the variable capacity compressor system andconfigured to adjust a superheat target setpoint of the refrigerantwithin the refrigerant circuit based on the data.
 2. The refrigerationsystem of claim 1, further comprising a condenser disposed along therefrigerant circuit, wherein the controller is configured to adjustoperation of the condenser in response to adjustment of the superheattarget setpoint.
 3. The refrigeration system of claim 2, wherein thecondenser comprises a fan, wherein the controller is configured toadjust operation of the fan to adjust operation of the condenser.
 4. Therefrigeration system of claim 3, wherein the condenser comprises aplurality of fans comprising the fan, wherein the controller isconfigured to reduce a speed of the fan or suspend operation of the fanto adjust operation of the condenser.
 5. The refrigeration system ofclaim 1, wherein the superheat target setpoint comprises a target amountof superheat of the refrigerant between an evaporator disposed along therefrigerant circuit and the variable capacity compressor system.
 6. Therefrigeration system of claim 5, wherein the controller is configured toadjust the superheat target setpoint of the refrigerant based on asaturation temperature of the refrigerant at the operating capacity. 7.The refrigeration system of claim 1, wherein the superheat targetsetpoint comprises a target superheated temperature of the refrigerantbetween an evaporator disposed along the refrigerant circuit and thevariable capacity compressor system.
 8. The refrigeration system ofclaim 1, wherein the variable capacity compressor system comprises aplurality of compressors, wherein the operating capacity of the variablecapacity compressor system is based on a respective capacity of eachcompressor of the plurality of compressors in operation.
 9. Therefrigeration system of claim 8, wherein a first compressor of the firstplurality of compressors has a first capacity, a second compressor ofthe plurality of compressors has a second capacity, and the firstcapacity and the second capacity are different from one another.
 10. Therefrigeration system of claim 1, wherein the controller is configured toadjust the operating capacity based on a detected ambient temperature.11. A control system configured to control operation of a vaporcompression system, wherein the control system comprises a memory deviceand a processor, and wherein the memory device includes instructionsthat, when executed by the processor, cause the processor to: adjust anoperating capacity of a variable capacity compressor system disposedalong a refrigerant circuit of the vapor compression system; and adjusta superheat target setpoint of a refrigerant flowing through therefrigerant circuit based on the operating capacity.
 12. The controlsystem of claim 11, wherein the superheat target setpoint comprises atarget superheated temperature of the refrigerant at a location alongthe refrigerant circuit between the variable capacity compressor systemand an evaporator disposed along the refrigerant circuit.
 13. Thecontrol system of claim 11, wherein the superheat target setpointcomprises a target amount of superheat of the refrigerant at a locationalong the refrigerant circuit between the variable capacity compressorsystem and an evaporator disposed along the refrigerant circuit.
 14. Thecontrol system of claim 11, wherein the instructions, when executed bythe processor, cause the processor to adjust operation of the vaporcompression system based on the superheat target setpoint.
 15. Thecontrol system of claim 14, wherein the instructions, when executed bythe processor, cause the processor to adjust operation of a condenserfan of a condenser disposed along the refrigerant circuit based on thesuperheat target setpoint.
 16. The control system of claim 11, whereinthe variable capacity compressor system comprises a plurality ofcompressors, and wherein the instructions, when executed by theprocessor, cause the processor to suspend operation of a firstcompressor of the plurality of compressors and initiate operation of asecond compressor of the plurality of compressors to adjust theoperating capacity of the variable capacity compressor system.
 17. Thecontrol system of claim 11, wherein the instructions, when executed bythe processor, cause the processor to adjust the operating capacity ofthe variable capacity compressor system based on a cooling demand of thevapor compression system.
 18. The control system of claim 11, whereinthe instructions, when executed by the processor, cause the processor toadjust the superheat target setpoint based on feedback from sensorsdisposed along the refrigerant circuit, wherein the feedback isindicative of an operating parameter of the refrigerant.
 19. A vaporcompression system, comprising: a condenser disposed along a refrigerantcircuit and configured to condense a refrigerant flowing through therefrigerant circuit; a variable capacity compressor system disposedalong the refrigerant circuit and configured to pressurize therefrigerant supplied to the condenser; and a controller configured toadjust a superheat target setpoint of the refrigerant based on anoperating capacity of the variable capacity compressor system.
 20. Thevapor compression system of claim 19, wherein the controller isconfigured to adjust operation of the condenser based on the superheattarget setpoint.
 21. The vapor compression system of claim 20, whereinthe controller is configured to adjust operation of a condenser fan ofthe condenser based on the superheat target setpoint.
 22. The vaporcompression system of claim 21, wherein the controller is configured toreduce a speed of the condenser fan or suspend operation of thecondenser fan based on the superheat target setpoint.
 23. The vaporcompression system of claim 19, further comprising a sensor disposedalong the refrigerant circuit, wherein the sensor is configured todetect an operating parameter of the refrigerant, and wherein thecontroller is configured to adjust the operation of the vaporcompression system based on the operating parameter and based on thesuperheat target setpoint.
 24. The vapor compression system of claim 19,wherein the superheat target setpoint comprises an amount of superheatof the refrigerant at a location along the refrigerant circuit betweenthe variable capacity compressor system and an evaporator disposed alongthe refrigerant circuit.
 25. The vapor compression system of claim 19,wherein the superheat target setpoint comprises a superheatedtemperature of the refrigerant at a location along the refrigerantcircuit between the variable capacity compressor system and anevaporator disposed along the refrigerant circuit.